obstinate; stubborn; refusing to change one's opinion or attitude — often with a slightly negative nuance.
彼は意固地になって誰の助言も聞かなかった。
He became obstinate and didn't listen to anyone's advice.
意固地な態度は人間関係を悪くすることがある。
A stubborn attitude can sometimes damage relationships.
そんなに意固地に張り合わなくてもいいよ。
You don't have to be so stubbornly competitive.